Experimental determination of the fracture toughness via microscratch tests: Application to polymers, ceramics, and metals

Abstract

The MIT Faculty has made this article openly available. Please share how this access benefits you. Your story matters.This article presents a novel microscratch technique for the determination of the fracture toughness of materials from scratch data. While acoustic emission and optical imaging devices provide quantitative evidence of fracture processes during scratch tests, the technique proposed here provides a quantitative means to assess the fracture toughness from the recorded forces and depth of penetration. We apply the proposed method to a large range of materials, from soft (polymers) to hard (metal), spanning fracture toughness values over more than two orders of magnitude. The fracture toughness values so obtained are in excellent agreement with toughness values obtained for the same materials by conventional fracture tests. The fact that the proposed microscratch technique is highly reproducible, almost nondestructive, and requires only small material volumes makes this technique a powerful tool for the assessment of fracture properties for microscale materials science and engineering applications.

A Novel Methods for Fracture Toughness Evaluation of Tool Steels with Post-Tempering Cryogenic Treatment

“…Before the test, the surface samples were prepared per the procedure described by Akono et al in [21]. The specimens were tested with a 200 µm Rockwell C diamond indenter at a scratching speed of 6 mm/min with vertical force equal to 30 N, and the scratch length was 6 mm.…”

“…Akono et al in [20] proposed an alternative novel technique to measure the fracture toughness by scratch testing. The authors derived the fracture toughness expression from linear elastic fracture mechanics, and in [21] applied these techniques to ceramics, metals, polymers, and in [22], to micro-particulate composites. Akono et al in [21] proposed a detailed description of an analytical model (with theoretical hypothesis and pertinence), materials surface preparation (the same for nano-indentation or micro-indentation), and the equipment and testing procedure, and showed that the Kc values measured via scratch test were in agreement with literature values, with a relative error of 2%-8% for ceramics and 3%-7% for metals.…”

A Novel Methods for Fracture Toughness Evaluation of Tool Steels with Post-Tempering Cryogenic Treatment

“…Before the test, the surface samples were prepared per the procedure described by Akono et al in [21]. The specimens were tested with a 200 μm Rockwell C diamond indenter at a scratching speed of 6 mm/min with vertical force equal to 30 N, and the scratch length was 6 mm.…”

Experimental chemo-mechanics of early-age fracture properties of cement paste

“…Scratch force criteria as a basis for comparison of scratch resistance of materials emerged throughout the 20th century, leading to the development of instrumented scratch tests in the early 1970s, in which the applied forces and acoustic emissions generated by microcracks are measured simultaneously [18]. The scratch test is highly sought after as a means of classification of materials due to its simplicity (it is almost noninvasive) and ease of application to only a small amount of many different materials including metals [19], polymers [20][21][22][23][24], rocks [25][26][27][28][29], ceramics [30][31][32], coatings and adhesion of thin films [33][34][35][36][37], and hardened cement pastes and cement slurries [38][39][40][41][42][43].…”

“…Based on Linear Elastic Fracture Mechanics (LEFM), the model here employed resolves the micro-scratch fracture toughness K c from the measured scratch force history, F T , and penetration depths d collected during the test [21,39,45] (for further discussion of relevance of LEFM for scratch application, see discussion in [46,47]):…”